Can a more streamlined shape of SSO as well as WK reduce air-caused frictions and increase end velocity?

Can SSO's concept be modified to leave SSO's engine empty of propellant until WK has arrived launch altitude and fuel the engine after reaching that altitude? Or is that impossible because of the propellant being solid? If yes the vehicle could be larger - especially it could have a larger tank or more tanks which means more propellant fueled at launch altitude. That can increase apogee altitude, velocity or payload capacity.

if the SSX (probably 2-3) was big enough, there COULD be some advantage from the fact that WK could carry the oxidizer in some place to spread the weight out more advantageously, but that seems very unlikely, and i agree that it's really an issue of KISS. it's not like the ship'd save any mass that way....

The idea is to leave SSO's tank empty as long as WK hasn't reached launch altitude and SSO isn't going to ignite its engine.

In that case SSO is lighter than during the XPRIZE launches. But it doesn't need to - so the empty tank could be designed more voluminous. That would provide higher altitude, more speed etc. after fueling at launch altitude before ignition.

The extra aircraft could be very similar to normal small aircrafts able to reach the launch altitude of SSO. The technology for fueling in the air is well known today and there are many experiences. As far as I know only the air forces are using it. They are providing much more propellant this way than required for SSO during the two XPRIZE flights. So the fueling aircraft could be smaller than those of the air forces. Perhaps it could be unmanned - and it may be that the genius of Burt Rutan would find improvements that increase safety and security to the required levels.

Perhaps such a way woul increase simplicity.

There is one XPRIZE team that has been working on a concept similar to this - that concept has been called "one stage and a half".

Reality check. Nitrous oxide is stored at almost 50 bar pressure, there is absolutely no way nitrous could be transferred in-flight. The only current rocket oxidizer that could is hydrogen peroxide, and SSO does not use it.

There are very few "normal small airplanes" that could touch the launch altitude of SSO, and those that do are quite expensive bizjets.

The fact is, the more airplanes there is, the more expensive and complicated it is going to get.

Might it be advantegous regarding heating at reentry if the vehicle would be a torus-like object to some degree?

In that case less plasma woud have to pass the outer parts of current vehicles - a portion would pass a channel thruoght the inner. This woud mean even more surface the heat can be distributed or spread over without making the vehicle longer.

If that is thinkable what effect might it have on drag and braking? And would it provide opportunities to gather a bit of the plasma for any purpose?